If I increase my suction from 3/4 to 7/8, do I need to increase my liquid line to? Going 70 ft. to attic. Thanks

What ton unit? And how many ft of vertical run?

2.5 ton, 50 ft. vertical

This may also require a crankcase heater and a hard start kit.

I would say 7/8 - 3/8 should do this OK with a 2.5 unit.

Thanks for the input, some people even go so far as putting a suction accumulator or liq. Solenoid.

A suction accumulator would also be a very good idea.

For a super deluxe job a receiver (if the condenser is not large enough to take all the liquid) and a pump down solenoid will control the weight of the column of liquid refrigerant upon shut down. This will prevent compressor oil wash out from the bearings etc.

Quick Facts: Migration And Pump Down Systems - Service and Maintenance - Extra Edition - Air Conditioning, Heating & Refrigeration NEWS (http://www.achrnews.com/Articles/Service_and_Maintenance/69f79d2d1116a010VgnVCM100000f932a8c0____)

While possibly not critical there will also be a loss of cooling capacity due to the 50 foot height.

Meier Supply - Pump Down (http://www.meiersupply.com/MSTipsPumpDown.htm)

Liquid slug or liquid in the crankcase will kill a compressor quickly so doing the job correctly will have many benefits.